Oxidative/reductive methods of deaggregation of electrically conductive polymers and precursors thereof and methods of fabricating articles therewith

ABSTRACT

The present invention is directed to oxidative and reductive methods of fabricating electrically conducting polymers and precursors thereof in particular polyanilines in which the polymer chains are deaggregated. Such deaggregated conducting polymers and precusors thereof exhibit better processability and higher electrical conductivity than do the corresponding aggregated polymers. Substituted and unsubstituted polyanilines in the substantially non oxidized or non reduced form (emeraldine form) are converted to an intermediate deaggregated reduced or oxidized form. The intermediate reduced or oxidized deaggregated form is processed into an article. The articles is subsequently treated with a dopant and an oxidizing or reducing agent to reform the original substantially non oxidized or non reduced form. The methods described herein permit the formation of articles such as shaped articles and films having deaggregated structure and higher electrical conductivity.

CROSS REFERENCE TO RELATED APPLICATION

This application is a International 371 of PCT/US97/19378 filed Jul. 24,1997 and also claims priority from Provisional Application U.S. Ser. No.60/022,706 which was filed on Jul. 25, 1996.

The teaching of U.S. application Ser. No. 09/043623, filed on the sameday herewith entitled, "VIBRATIONAL METHODS OF DEAGGREGATION OFELECTRICALLY CONDUCTIVE POLYMERS AND PRECURSORS THEREOF" to M.Angelopoulos et al. is incorporated herein by reference.

The teaching of U.S. application Ser. No. 09/043,630, filed on the sameday herewith entitled, "CONTROL OF POLYMERIZATION KINETICS AND RATE OFPOLYMER PRECIPITATION AS A MEANS OF CONTROLLING THE AGGREGATION ANDMORPHOLOGY IN CONDUCTIVE POLYMERS AND PRECURSORS THEREOF" to M.Angelopoulos et al. is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to oxidative and reductive methods offabricating electrically conducting polymers and precursors thereof andmethods of fabricating articles therewith in which the polymer chainsare deaggregated. Such deaggregated conducting polymers and precursorsthereof exhibit better processability and higher electrical conductivitythan do the corresponding aggregated polymers.

BACKGROUND OF THE INVENTION

Electrically conductive organic polymers have been of scientific andtechnological interest since the late 1970's. These relatively newmaterials exhibit the electronic and magnetic properties characteristicof metals while retaining the physical and mechanical propertiesassociated with conventional organic polymers. Herein we describeelectrically conducting polymers, for example polyparaphenylenevinylenes, polyparaphenylenes, polyanilines, polythiophenes, polyazines,polyfuranes, polypyrroles, polyselenophenes, poly-p-phenylene sulfides,polythianapthenes, polyacetylenes formed from soluble precursors,combinations thereof and blends thereof with other polymers andcopolymers of the monomers thereof.

These polymers are conjugated systems which are made electricallyconducting by doping. The non-doped or non-conducting form of thepolymer is referred to herein as the precursor to the electricallyconducting polymer. The doped or conducting form of the polymer isreferred to herein as the conducting polymer.

Conducting polymers have potential for a large number of applications insuch areas as electrostatic charge/discharge (ESC/ESD) protection,electromagnetic interference (EMI) shielding, resists, electroplating,corrosion protection of metals and ultimately metal replacements, i.e.wiring, plastic microcircuits, conducting pastes for variousinterconnection technologies (solder alternative) etc.. Many of theabove applications especially those requiring high current capacity havenot yet been realized because the conductivity of the processableconducting polymers is not yet adequate for such applications. In orderfor these materials to be used in place of metals in more applications,it is desirable to increase the conductivity of these materials. Inaddition, the processability of these polymers also requiresimprovement. Although some of these polymers are soluble, the solubilityis generally limited and the solutions tend to be not stable over time.

The polyaniline class of conducting polymers has been shown to be one ofthe most promising and most suited conducting polymers for a broad rangeof commercial applications. The polymer has excellent environmentalstability and offers a simple, one-step synthesis. However, theconductivity of the material in its most general form (unsubstitutedpolyaniline doped with hydrochloric acid) is generally on the low end ofthe metallic regime most typically, on the order of 1 to 10 S/cm (A. G.Macdiarmid and A. J. Epstein, Faraday Discuss. Chem. Soc. 88, 317,1989). In addition, the processability of this class of polymersrequires improvement. Although polyaniline is a soluble polymer, it hasbeen noted that the solutions tend to be unstable with time. (E. J. OHet al, Synth. Met. 55-57, 977 (1993). Solutions of for example thepolyaniline in the non-doped form tend to gel upon standing. Solutionsgreater than 5% solids concentration tend to gel within hours limitingthe applicability of the polymer. It is desirable to devise methods ofincreasing the electrical conductivity of the doped polyanilines and toenhance the processability of these systems to allow broaderapplicability.

The conductivity (σ) is dependent on the number of carriers (n) set bythe doping level, the charge on the carriers (q) and on the mobility (g)(both interchain and intrachain mobility) of the carriers.

    σ=n q μ

Generally, n (the number of carriers) in these systems is maximized andthus, the conductivity is dependent on the mobility of the carriers. Toachieve higher conductivity, the mobility in these systems needs to beincreased. The mobility, in turn, depends on the morphology of thepolymer. The intrachain mobility depends on the degree of conjugationalong the chain, presence of defects, and on the chain conformation. Theinterchain mobility depends on the interchain interactions, theinterchain distance, and the degree of crystallinity. Thus, theconductivity is very dependent on the morphology of the polymer.

Recently, it has been shown that polyaniline in the non-doped form has atendency to aggregate as a result of interchain hydrogen bonding andthat this aggregation limits the solvation of the polymer (U.S.application Ser. No. 08/370,127 filed on Jan. 9, 1995 and U.S.application Ser. No. 08/370,128 filed on Jan. 9, 1995, the teachings ofwhich are incorporated herein by reference). It was found that certainadditives such as lithium chloride could be added to the polyaniline todisrupt the aggregation. As the aggregation was disrupted, the chainsbecame disentangled from each other and the solvent was able to moreeffectively solvate the chains to adapt a more expanded chainconformation. As a result, the deaggregated polymer upon dopingexhibited higher levels of conductivity than did the polymer in theaggregated form. In addition, it was found that the deaggregatedsolutions were more stable with time than the corresponding aggregatedsolutions.

Herein novel methods of deaggregating conducting polymers are describedwhich involve oxidation and reduction reactions.

OBJECTS

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymers.

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymersso that the molecules can be more uniformly doped.

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymersso that the molecules can exhibit high conductivity upon doping.

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymersso that the molecules can exhibit good processability and good solutionstability.

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymersso that the molecules can be more effectively processed into articles,such as films, fibers, or any structural form or shaped article.

It is an object of the present invention to deaggregate aggregatedmolecules which are precursors to the electrically conducting polymersso that the molecules can be more effectively processed into films,fibers, or any structural form having tunable morphology andmechanical/physical properties.

It is an object of the present invention to deaggregate aggregatedmolecules which are electrically conducting polymers.

It is an object of the present invention to deaggregate aggregatedmolecules which are electrically conducting polymers so that themolecules can exhibit good processability and good solution stability.

It is an object of the present invention to deaggregate aggregatedmolecules which are electrically conducting polymers so that themolecules can be more effectively processed into films, fibers, or anystructural form.

It is an object of the present invention to deaggregate aggregatedmolecules which are electrically conducting polymers so that themolecules can be more effectively processed into films, fibers, or anystructural form having tunable morphology and mechanical/physicalproperties.

It is an object of the present invention to increase the electricalconductivity of electrically conductive polymers.

It is another object of the present invention to increase the electricalconductivity of electrically conductive polymers by extending theelectrically conductive regions or islands of the electricallyconductive polymer.

It is another object of the present invention to further increase theelectrical conductivity of a deaggregated electrically conductivepolymer by stretch orientation.

SUMMARY OF THE INVENTION

A broad aspect of the present invention is a method for fabricatingelectrically conducting polymers and precursors to electricallyconducting polymers that are deaggregated. The deaggregated polymersexhibit increased solubility and processability, higher conductivityupon doping, and more uniform doping than do the correspondingaggregated polymers.

A more specific aspect of the present invention is a method of reducingor oxidizing substantially nonreduced or nonoxidized precursor polymersto an electrically conductive polymer in aggregated form to a reduced oroxidized deaggregated intermediate form which is formed into an articleand subsequently doped and oxidized or reduced back to a nonreduced ornonoxidized form to result in a polymer having higher electricalconductivity than if the nonreduced or nonoxidized precusor is dopedwithout first being reduced or oxidized.

A more specific aspect of a method of the present invention isdeaggregating the precursor polymer or electrically conducting polymereither in solution or in the solid state by an oxidation or reductionreaction, the oxidation and reduction reaction preferably beingchemically or electrochemically accomplished.

Another more specific aspect of a method of the present inventionincludes steps of providing a precursor to an electrically conductingpolymer either in the solid state form such as a powder, film, fiber orstructural part, or in solution; oxidizing or reducing the precursor bya chemical or electrochemical reaction thereby converting precursor toan oxidized or reduced form; adding a dopant to the oxidized or reducedprecursor polymer; converting precursor polymer to original non-reducedor non-oxidized state. The dopant can be added to the oxidized orreduced polymer before the oxidized or reduced polymer is converted tothe original non- reduced or non-oxidized form. Alternatively, thedopant can be added to the oxidized or reduced polymer after theoxidized or reduced polymer is converted to the original non-reduced ornon- oxidized form. Alternatively, the dopant can be added to theoxidized or reduced polymer at the same time that the oxidized orreduced polymer is converted to the original non-reduced or non-oxidized form.

Another more specific aspect of a method of the present inventionincludes steps of providing a precursor to an electrically conductingpolymer in solution; oxidizing or reducing the precursor in solution bya chemical or electrochemical reaction thereby converting precursor toan oxidized or reduced form; processing the solution of reduced oroxidized polymer into a powder, film, fiber, or structural part; dopingand converting the precursor polymer to original non-reduced ornon-oxidized state. The dopant can be added to the oxidized or reducedpolymer before the oxidized or reduced polymer is converted to theoriginal non-reduced or non-oxidized form. Alternatively, the dopant canbe added to the oxidized or reduced polymer after the oxidized orreduced polymer is converted to the original non- reduced ornon-oxidized form. Alternatively, the dopant can be added to theoxidized or reduced polymer at the same time that the oxidized orreduced polymer is converted to the original non-reduced or non-oxidizedform.

Another more specific aspect of a method of the present inventionincludes steps of providing an electrically conducting polymer either inthe solid state form such as a powder, film, fiber or structural part,or in solution; oxidizing or reducing the electrically conductingpolymer by a chemical or electrochemical reaction thereby converting thepolymer to an oxidized or reduced form; converting the polymer tooriginal non-reduced or non-oxidized state.

Another more specific aspect of a method of the present inventionincludes steps of providing an electrically conducting polymer insolution; oxidizing or reducing said polymer in solution by a chemicalor electrochemical reaction thereby converting polymer to an oxidized orreduced form; processing said solution of reduced or oxidized polymerinto a powder, film, fiber, or structural part; converting said polymerto original non-reduced or non-oxidized state.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features, and advantages of the present invention willbecome apparent from a consideration of the following detaileddescription of the invention when read in conjunction with the drawingFIGS., in which:

FIG. 1 is a general formula for a polyaniline; (a) is the precursor formof the polymer or the non-doped form of the polymer; (b) is the dopedform of the polymer or the electrically conducting form of polyaniline;(c) is the actual structure for the doped electrically conductingpolymer consisting of a polysemiquinone radical cation.

FIG. 2 depicts interchain hydrogen bonding in emeraldine base between anamine site of one chain and an imine site of a second chain.

FIG. 3 depicts gel permeation chromatographs (GPC) of polyaniline basein the emeraldine base in NMP (a); of partly reduced emeraldine base inNMP by the addition of hydrazine (b); and more fully reduced emeraldinebase in NMP by the addition of more hydrazine (c). As can be seen, thehigh molecular weight fraction decreases as the polymer is more fullyreduced.

FIG. 4 depicts infra-red spectra for a polyaniline base in the reduced,leucoemeraldine base form, and for the emeraldine base form.

FIG. 5 depicts the changes in the infra-red spectra observed as theemeraldine base is reduced to the leucoemeraldine base. (a) emeraldinebase film (b) film after treatment with hydrazine vapor for 15 minutes(c) film after treatment with hydrazine vapor for 30 minutes (d) filmafter treatment with hydrazine vapor for 1 hour and (e) film aftertreatment with hydrazine vapor for 12 hours. As can be seen, theH-bonded N--H stretching band decreases as the emeraldine base polymeris reduced.

DETAILED DESCRIPTION

The present invention is directed to methods of deaggregatingelectrically conducting polymer precursors and electrically conductingpolymers. Examples of such polymers are of substituted and unsubstitutedpolyparaphenylenes, polyparaphenylevevinylenes. polyanilines,polyazines, polythiophenes, polythianaphthenes, poly-p-phenylenesulfides. polyfuranes, polypyrroles, polyselenophenes, polyacetylenesformed from soluble precursors and combinations thereof and copolymersof monomers thereof. The general formula for these polymers can be foundin U.S. Pat. No. 5,198,153 to Angelopoulos et al. the teaching of whichis incorporated herein by reference. The present invention is mostsuitable to one class of polymers which are substituted or unsubstitutedpolyaniline or copolymers of polyaniline having general formula shown inFIG. 1 wherein each R can be H or any organic or inorganic radical; eachR can be the same or different; wherein each R¹ can be H or any organicor inorganic radical, each R¹ can be the same or different; x≧1;preferably x>2 and y has a value from 0 to 1. Examples of organicradicals are alkyl or aryl radicals. Examples of inorganic radicals areSi and Ge. This list is exemplary only and not limiting.

The precursor to the electrically conducting polymer form is shown inFIG. 1a. This is the non-doped form of the polymer or the base polymer.FIG. 1b shows polyaniline doped with a dopant. If the polyaniline baseis exposed to cationic species QA, the nitrogen atoms of the imine partof the polymer becomes substituted with the Q+ cation to form anemeraldine salt as shown in FIG. 1b. Q+ can be selected from H+ andorganic or inorganic cations, for example, an alkyl group or a metal.

QA can be a protic acid where Q is hydrogen. When a protic acid HA isused to dope the polyaniline, the nitrogen atoms of the imine part ofthe polyaniline are protonated. The emeraldine base form is greatlystabilized by resonance effects. The charges distribute through thenitrogen atoms and aromatic rings making the imine and amine nitrogensindistinguishable. The actual structure of the doped form is adelocalized polysemiquinone radical cation as shown in FIG. 1c.

Polyaniline can exist in a number of oxidation states. The emeraldineform of the polymer refers to the material that consists ofapproximately equal number of benzenoid units and quinoid units (y=≅0.5in FIG. 1). The emeraldine polymer can be reduced to the leucoemeraldinepolymer where y=1 in FIG. 1. The leucoemeraldine base form of thepolymer is not stable in ambient conditions. The emeraldine polymer canbe oxidized to the pernigraniline form where y=0; however, the fullyoxidized form of the polymer also tends not to be stable. In principle,other oxidation states intermediate between y=0 and y=1 are possible.The emeraldine base form of the polyaniline is the most stable form.Because of its environmental stability, it is the form of polyanilinethat has been the most abundantly studied and is the form that is suitedfor technological applications.

The emeraldine base form of polyaniline is soluble in various organicsolvents and in various aqueous acid solutions. Examples of organicsolvents are dimethylsulfoxide (DMSO), dimethylformamide (DMF),N-methylpyrrolidinone (NMP), N,N'-dimethyl propylene urea (DMPU),pyridine, m-cresol, phenol and so on. This list is exemplary only andnot limiting. Examples of aqueous acid solutions is aqueous acetic acidand formic acid solutions. This list is exemplary only and not limiting.

Previously we disclosed (U.S. Ser. No. 08/370,127 filed on Jan. 9, 1995and U.S. application Ser. No. 08/370,128 filed on Jan. 9, 1995, theteachings of which are incorporated herein by reference.) thatpolyaniline in the emeraldine base form aggregates as a result ofinterchain hydrogen bonding between the amine and imine sites as shownschematically in FIG. 2. These aggregates were evidenced by a bimodalmolecular weight distribution in gel permeation chromatography.Emeraldine base in NMP for example exhibits a bimodal distribution as isshown in FIG. 3a. In this particular chromatograph, the area of the highmolecular weight fraction is on the order of 6%. This high molecularweight fraction is due to chain aggregation resulting in "pseudo" highmolecular weights. Previously we disclosed that certain additives suchas lithium chloride could be added to these solutions to disrupt thehydrogen bonding and in turn reduce or eliminate the high molecularweight fractions. Herein, we disclose novel methods of disrupting theaggregation of emeraldine base which involves first reducing oroxidizing the emeraldine base to a different oxidation state and thenprocessing the material in this form followed by conversion to itsoriginal environmentally stable emeraldine form.

It is found that upon reduction of emeraldine base towards theleucoemeraldine form, the high molecular weight fraction in the GPCdecreases as is shown in FIGS. 3b and c. Hydrazine, a reducing agent, isadded to the emeraldine base solution in various amounts. The partlyreduced product is titrated to determine its oxidation state. Thechromatographs depicted in FIGS. 3b and 3c correspond to a reducedpolyaniline in which 1-y=0.4 and 1-y=0.3 in equation shown in FIG. 1. Ascan be seen, as the polyaniline in the emeraldine base form is reduced,the high molecular weight fraction dramatically decreases indicatingthat the aggregation is disrupted.

FIG. 4 depicts the infra-red (IR) spectrum for the polyaniline,emeraldine base powder (b) and for a fully reduced, leucoemeraldine basepolymer (a). The IR shows two distinct N--H stretching bands for theemeraldine base--a major broad band located at 3290 cm-1 and a minorsharp band located at 3383 cm-1. In contrast, the spectrum ofleucoemeraldine base shows only one sharp N--H band located at 3384 cm-1associated with a free (non-hydrogen bonded) N--H stretching vibration.The band at 3290 seen in emeraldine base is due to a hydrogen-bondedN--H stretching vibration.

Emeraldine base is a mixed oxidation state polymer containing amine andimine sites whereas leucoemeraldine base contains only amine sites. Theinfra-red data shows that the hydrogen-bonding between amine and iminesites is stronger than amine-amine hydrogen bonding and thus significanthydrogen-bonding and in turn aggregation is observed in emeraldine basewhereas no significant hydrogen-bonding and in turn aggregation isobserved in leucoemeraldine base. FIG. 5 shows that as an emeraldinebase film is treated to hydrazine vapor in-situ, a progressive markeddecrease in the hydrogen-bonded N--H stretching band is observed with aconcomitant increase in the free N--H stretch.

Oxidation of emeraldine base to the pernigraniline form which results inonly imine sites on the polymer backbone also eliminates hydrogenbonding and thus, aggregation. Although the aggregation of emeraldinebase is eliminated upon reduction to the leucoemeraldine form or uponoxidation to the pernigraniline form, the polymer can not in practice beused in these forms as they are unstable in ambient conditions. Inaddition, doping of leucoemeraldine base or pernigraniline base does notproduce a significantly conducting form. It is the polymer in theemeraldine form that gives the highest conductivity to date as comparedto the other oxidation states.

The aggregation in emeraldine base limits the solubility of the polymer.The more aggregated the emeraldine base, the less soluble is thepolymer. In addition, the aggregation induces the solutions of thispolymer to gel especially at concentrations above 5%. Thus, thesolutions of aggregated emeraldine base are not stable. Furthermore, theaggregation in emeraldine base limits the doping uniformity andefficiency; it also limits the conductivity; and prevents the chainsfrom adapting a crystalline structure.

Thus, it is important to reduce the aggregation of emeraldine base butto be able to maintain the polymer in this oxidation state in the end.What is needed is for emeraldine base to be able to be first convertedto a transient form, i.e. the reduced or oxidized form, but then to beable to reconvert back to the emeraldine polymer without having thepolymer reaggregate in the process. This can be done in several methods.First the emeraldine base in the solid state, e.g. powder, film, fiber,structural part or in solution is reduced to the leucoemeraldine form oroxidized to the pernigraniline form by the addition of a reducing agentor oxidizing agent respectively or electrochemically by the applicationof appropriate potential. The transient leucoemeraldine/pernigranilineform of the polymer is then treated with a dopant suitable for theemeraldine base and reoxidized or rereduced by treatment with a reducingagent or oxidizing agent or electrochemically to isolate the dopedemeraldine deaggregated polymer. The dopant and oxidizing/reducing agentused to reform the emeraldine polymer can be added together or thedopant can be added first followed by the redox reagent. To preventreaggregation it is not desirable to add the redox reagent first priorto the dopant. Otherwise, the polymer in the non-doped emeraldine basewill reform and can reaggregate in the process. In the preferredembodiment, the reduced or oxidized form of the polymer is treated witha dopant followed by the oxidizing or reducing agent. In this fashion,as the emeraldine polymer is formed, it will be formed in the dopedform. In the doped form, the imine sites are reacted and are notavailable for hydrogen bonding.

A second method involves forming an emeraldine base solution. To thissolution is added a reducing agent or an oxidizing agent or is treatedelectrochemically by applying a potential to convert the polymer insolution to the leucoemeraldine base or to the pernigraniline base. Thissolution is then processed into a film, fiber, or a structural part. Theprocessed film, fiber, structural part is then treated with a dopant andan oxidant or reducing agent to reform the doped emeraldine form of thepolymer.

A third method involves taking the doped emeraldine salt in the solidstate form, i.e. powder, film, fiber, or structural part or in solutionand reducing the doped polymer or oxidizing the doped polymer ortreating it electrochemically to form the leucoemeraldine orpernigraniline form in the presence of the dopant. The reduced oroxidized form of the polymer is then reconverted to the emeraldinepolymer. While in the reduced or oxidized form, the polymer in solutionor powder or film or fiber or structural part could be processed furtherby thermal or mechanical processing prior to the conversion to theemeraldine form.

The emeraldine form in which y=≅0.5 in FIG. 1 can be reduced or oxidizedas above but the reduction or oxidation does not need to go tocompletion, i.e. reaching y=1 or y=0. The fully reduced polymer (y=1)and the fully oxidized polymer (y=0) exhibit the least aggregation andis the preferred method, however, reduction of emeraldine base to levelsless than y=0.5 or oxidation to levels above y=0.5 will reduce theaggregation to some extent; the more reduced or more oxidized it is themore deaggregated the structure. This was seen in FIG. 3 where reducedlevels of 1-y=0.4 or y=0.6 and 1=y=0.3 or y=0.7 are reached andsignificant reduction in aggregation is observed. The degree ofoxidation/reduction is controlled by the amount of oxidizing or reducingagent that is added and also by the amount of time the reaction isallowed to take place and on the reaction conditions.

An exemplary list of reducing agents include hydrazine, phenylhydrazine,other substituted hydrazines, titanium chloride, hydrogen,lithiumaluminum hydride, zinc, raney nickel, and so on. An exemplary list ofoxidizing agents include FeCl₃, hydrogen peroxide, oxygen, periodatessuch as sodium periodate, chromates such as potassium dichromate,ammonium peroxydisulfate, peracids such m-chloroperoxybenzoic acid leadacetate and so on. The oxidation/reduction can also be carried outelectrochemically by the application of a potential.

An exemplary list of solvents useful to practice the present inventionis:

N-methyl pyrrolidinone (NMP)

dimethyl sulfoxide (DMSO)

dimethyl formamide (DMF)

pyridine

toluene

xylene

m-cresol

phenol

dimethylacetamide

tetramethylurea

n-cyclohexylpyrrolidinone

aqueous acetic acid

aqueous formic acid

pyrrolidinone

N, N' dimethyl propylene urea (DMPU)

benzyl alcohol

water

An exemplary list of dopants which can be used to dope the polymer tothe conducting state are: hydrochloric acid, acetic acid, formic acid,oxalic acid, toluenesulfonic acid, dodecylbenzene sulfonic acid,benzenesulfonic acid, naphthalene sulfonic acid, methyliodide andcamphor sulfonic acid, acrylamidopropanesulfonic acid, and so on.

EXAMPLES

The unsubstitued polyaniline in the emeraldine form is synthesized bythe chemical oxidative polymerization of aniline in IN HCl usingammonium peroxydisulfate as an oxidizer. Polyaniline can also beoxidatively polymerized electrochemically as taught by W. Huang, B.Humphrey, and A. G. MacDiarmid, J. Chem. Soc. Faraday Trans. 1,82, 2385,1986. In the chemical synthesis, the conducting polyanilinehydrochloride (emeraldine hydrochloride) salt precipitates fromsolution. The polymerization is allowed to proceed for several hoursafter which the powder is filtered, washed with excess 1N hydrochloricacid. The emeraldine hydrochloride is then converted to thenon-conducting or non-doped emeraldine base by reaction with 0.1Mammonium hydroxide. The emeraldine base is then filtered, washed withammonium hydroxide, then washed with methanol and dried. The polymer atthis stage is in the undoped emeraldine base form as a powder.

Substituted (either on the aromatic ring or on the nitrogen)polyanilines in the emeraldine form are synthesized in the same fashionas above but using the appropriate substituted aniline monomer in thepolymerization reaction. Copolymers are made by the oxidativepolymerization of one or more monomers. Other acids can also be used inthe polymerization reaction other than hydrochloric acid. Aqueous aceticacid, sulfuric acid, organic sulfonic acids, such as aqueoustoluenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid,and so on. The o-ethoxy substituted polyaniline was prepared byoxidative polymerization of o-ethoxy aniline in 1N hydrochloric acid asdescribed above. Copolymers having various amounts of o-ethoxy contentwere synthesized by polymerizing o-ethoxyaniline and aniline in aqueous1N hydrochloric acid. The amount of o-ethoxy content in the finalpolymer was controlled by varying the feed ratio of this monomer in theinitial polymerization reaction. Other ring substituted derivatives suchas o-hydroxyethyl ring substituted derivative as described in U.S.application Ser. No. 08/595,853 filed on Feb. 2, 1996 entitled"Cross-Linked Electrically Conductive Polymers and Precursors Thereof"and U.S. application Ser. No. 08/594,680 filed on Feb. 2, 1996 entitled"Methods of Fabricating Cross-Linked Electrically Conductive Polymersand Precursors Thereof" the teachings of which are incorporated hereinby reference.

The substituted and unsubstituted emeraldine base powder is generallyprocessed by dissolving the powder in an organic solvent. Theunsubstituted emeraldine base was dissolved in NMP at a 5-10%concentration. The solution was used to spin-coat films of theemeraldine base polymer on silicon wafers, quartz wafers, salt plates,and so on. These films were on the order of 500 A to 1.0 μm. Thickerfilms (on the order of 50 to 200 μm) were made by solution castingtechniques in which the solution was poured into an aluminum pan orglass dish and placed into a vacuum oven at 60° C. for 24 hours. Thesolution can also be used to process the material into a structural partor into a fiber. The substituted emeraldine base such as the o-ethoxysubstituted emeraldine base was more soluble than the unsubstitutedemeraldine base. This polymer can be dissolved in cyclohexanone,tetrahydrofuran, ethyllactate and so on. A solution was made incyclohexanone (5% solids) and this solution was used to process films(thin and thick).

Thin films of emeraldine base (substituted and unsubstituted) on quartzand salt plates were treated to hydrazine by exposing the films to thevapor of hydrazine. The films were exposed for various times. The longerthe films were exposed to hydrazine, the more reduced were the polymersas can be seen in FIG. 5 which depicts the infra-red changes that occurupon reduction for the unsubstituted emeraldine base case. As can beseen the hydrogen bonded N--H band is eliminated and a single N--Hstretching band is observed which is characteristic of theleucoemeraldine base. The emeraldine base powder was reduced by placingthe polymer in a hydrazine solution. Upon reduction, the excesshydrazine was extracted from the sample by washing with methanolfollowed by pumping under vacuum. Films of the emeraldine base can alsobe reduced by placing the films in a hydrazine solution. Alternatively,hydrazine can be added to a solution of the emeraldine base to reducethe polymer in solution. All the reduction reactions were done under aninert atmosphere (nitrogen). The degree to which the polymer was reducedwas controlled by the amount of hydrazine added and the time thereaction was allowed to take place. The degree of reduction in the finalpolymer was quantitatively determined by titration with an oxidizingagent such as potassium chromate.

The emeraldine polymer can also be oxidized in a similar fashion to thatdescribed above for the reduction case. The oxidizing agent can be irontrichloride, potassium chromate, and so on.

Once the emeraldine base is reduced either in the solid state form or insolution (under an inert atmosphere), a suitable dopant for theemeraldine form of the polymer such as a sulfonic acid, e.g. camphorsulfonic acid etc. is added followed by conversion of the reduced oroxidized form of the polymer back to the doped emeraldine form. Theconversion is done by treatment of the reduced polymer with an oxidizingagent and the oxidized polymer with a reducing agent. The dopant and thesuitable oxidizing agent or reducing agent can be added simultaneouslyto the reduced form or oxidized form of the polymer.

The doped emeraldine salt such as emeraldine hydrochloride, emeraldinetoluenesulfonate, emeraldine camphorsulfonate, and so on can also betreated with a reducing agent or oxidizing agent to convert the polymerto the reduced and oxidized polymer in the presence of the dopant. Sincethe dopant is already present, in order to reconvert the polymer back tothe emeraldine base, only an oxidizing agent or reducing agent needs tobe added. No dopant is necessary.

An Emeraldine base solution or an emeraldine salt solution is treatedwith hydrazine or hydrogen peroxide under an inert atmosphere to convertthe emeraldine base or salt to the reduced form or oxidized formrespectively. Once the reduced or oxidized form is generated, this formof the polymer is processed into-a film by solution casting methods,into a fiber, or into a structural part by thermal processing. Once ithas been processed, the doped emeraldine form is regenerated by suitableoxidation or reduction.

All references referred to herein are incorporated herein by reference.

While the present invention has been described with respect to preferredembodiments, numerous modifications, changes, and improvements willoccur to those skilled in the art without departing from the spirit andscope of the indention.

What is claimed is:
 1. A method comprising the following steps insequence:reducing or oxidizing a precursor to an electrically conductivepolymer in substantially nonreduced or non oxidized form to anintermediate reduced or oxidized form; forming a shaped article fromsaid intermediate reduced or oxidized form; exposing said shaped articleto a dopant oxidizing or reducing said shaped article to form a dopedarticle in substantially non oxidized or non reduced form.
 2. A methodaccording to claim 1 wherein said exposing of said article to a dopantis done before said oxidizing or reducing of said article.
 3. A methodaccording to claim 1 wherein said exposing of said article to a dopantis done after said oxidizing or reducing of said article.
 4. A methodaccording to claim 1 wherein said exposing of said article to a dopantis done at the same time as said oxidizing or reducing of said article.5. A method according to claim 1 wherein said forming of said article isdone after said exposing of said article to a dopant.
 6. A methodaccording to claim 1 wherein said forming of said article is done aftersaid exposing of said article to a dopant and after said said oxidizingor reducing said article.
 7. A method according to claim 1 wherein saidforming of said article is done before exposing said article to a dopantand before oxidizing or reducing said article.
 8. A method according toclaim 1 wherein said precursor to an electrically conductive polymer ispolyaniline in undoped from.
 9. A method according to claim 8 whereinsaid polyaniline in said nonreduced or nonoxidized form is in theemeraldine form.
 10. A method according to claim 1 wherein said articleis selected from the group consisting of a powder, a film, a fiber and astructural part.
 11. A method according to claim 1 wherein saidoxidizing is done by a process selected from the group consisting ofchemical oxidation and electrochemical oxidation.
 12. A method accordingto claim 1 wherein said reducing is done by a process selected from thegroup consisting of chemical reduction and electrochemical reduction.13. A method according to claim 11 wherein said chemical oxidation usesoxidation agents elected from the group consisting of hydrazine,phenylhydrazine, other substituted hydrazines, titanium chloride,hydrogen,lithium aluminum hydride, zinc and raney nickel.
 14. A methodaccording to claim 12 wherein said chemical reducing uses oxidationagents selected from the group consisting of FeCl3, hydrogen peroxide,oxygen, periodates, potassium dichromate, ammonium peroxydisulfate andperacids.
 15. A method according to claim 14 wherein said periodate issodium periodate.
 16. A method according to claim 14 wherein saidchromate is potassium dichromate.
 17. A method according to claim 1wherein said exposing of said article to a dopant is done before saidoxidizing or reducing of said article.
 18. A method according to claim 1wherein said exposing of said article to a dopant is done after saidoxidizing or reducing of said article.
 19. A method according to claim 1wherein said exposing of said article to a dopant is done at the sametime as said oxidizing or reducing of said article.
 20. A methodaccording to claim 1 wherein said forming of said article is done aftersaid exposing of said article to a dopant.
 21. A method according toclaim 1 wherein said forming of said article is done after said exposingof said article to a dopant and after said said oxidizing or reducingsaid article.
 22. A method according to claim 1 wherein said forming ofsaid article is done before exposing said article to a dopant and beforeoxidizing or reducing said article.
 23. A method according to claim 1wherein said precursor to an electrically conductive polymer ispolyaniline in undoped from.
 24. A method according to claim 23 whereinsaid polyaniline in said nonreduced or nonoxidized form is in theemeraldine form.
 25. A method according to claim 1 wherein said articleis selected from the group consisting of a powder, a film, a fiber and astructural part.
 26. A method according to claim 1 wherein saidoxidizing is done by a process selected from the group consisting ofchemical oxidation and electrochemical oxidation.
 27. A method accordingto claim 1 wherein said reducing is done by a process selected from thegroup consisting of chemical reduction and electrochemical reduction.28. A method according to claim 25 wherein said chemical oxidation usesoxidation agents elected from the group consisting of hydrazine,phenylhydrazine, other substituted hydrazines, titanium chloride,hydrogen,lithium aluminum hydride, zinc and raney nickel.
 29. A methodaccording to claim 27 wherein said chemical reducing uses oxidationagents selected from the group consisting of FeCl₃, hydrogen peroxide,oxygen, periodates, potassium dichromate, ammonium peroxydisulfate andperacids.
 30. A method according to claim 29 wherein said periodate issodium periodate.
 31. A method according to claim 29 wherein saidchromate is potassium dichromate.
 32. A method according to claim 29wherein said peracids are selected from the group consisting ofm-chloroperoxybenzoic acid and lead acetate.
 33. A methodcomprising:providing polyaniline in emeraldine form; reducing saidemeraldine form to a deaggregated leucoemeraldine form; forming anarticle from said deaggregated leucoemeraldine form; doping saiddeaggregated leucoemeraldine form; oxidizing said leucoemeraldine formto emeraldine form.
 34. A method comprising the following steps insequence:providing polyaniline in emeraldine form; oxidizing saidemeraldine form to a deaggregated pernigraniline form; forming a shapedarticle from said deaggregated pernigraniline form; doping saidpernigraniline form shaped article; reducing said deaggregatedpernigraniline form shaped article to emeraldine form shaped article.35. A method comprising:reducing or oxidizing a precursor to anelectrically conductive polymer in substantially nonreduced ornonoxidized form to an intermediate reduced or oxidized form; forming anintermediate reduced or oxidized form; exposing said intermediatereduced or oxidized form to a dopant; oxidizing or reducing saidintermediate reduced or oxidized form to form a doped polymer insubstantially nonoxidized or nonreduced form.
 36. A methodcomprising:reducing or oxidizing an electrically conductive polymer insubstantially nonreduced or nonoxidized form to an intermediate reducedor oxidized form; forming an intermediate reduced or oxidized form;oxidizing or reducing said intermediate reduced or oxidized form to forma doped polymer in substantially nonoxidized or nonreduced form.
 37. Amethod according to claim 35 wherein said intermediate reduced oroxidized form is in the solid state.
 38. A method according to claim 37wherein said solid state is selected from the group consisting of apowder, a film, a fiber and a structural part.
 39. A method according toclaim 38 wherein intermediate reduced or oxidized for is in solution.40. A method according to claim 35 further including forming an articlefrom said intermediate reduced or oxidized form.
 41. A method accordingto claim 36 wherein said intermediate reduced or oxidized form is in thesolid state.
 42. A method according to claim 41 wherein said solid stateis selected from the group consisting of a powder, a film, a fiber and astructural part.
 43. A method according to claim 36 wherein intermediatereduced or oxidized for is in solution.
 44. A method according to claim36 further including forming an article from said intermediate reducedor oxidized form.
 45. A method comprising: forming an emeraldine basesolution, adding to said emeraldine base solution a reducing agent or anoxidizing agent or treating said emeraldine base solutionelectrochemically by applying a potential to convert the emeraldinepolymer in solution to the leucoemeraldine base or to the pernigranilinebase in solution, said leucoemeraldine base or pernigraniline base insolution is then processed flito an article, said article is thentreated with a dopant and an oxidant or reducing agent to reform thedoped emeraldine form of the polymer.
 46. A method comprising: providinga doped emeraldine salt in the solid state form or in solution andreducing the doped polymer or oxidizing the doped polymer or treating itelectrochemically to form the leucoemeraldine or pernigraniline form inthe presence of a dopant, the reduced or oxidized form of the polymer isthen reconverted to the emeraldine polymer, while in the reduced oroxidized form, the polymer in solution or solid sate is processedfurther by thermal or mechanical processing prior to conversion to theemeraldine form.
 47. A method according to claim 1 wherein said polymeris a polyaniline having structural formula: ##STR1## wherein each R canbe H or any organic or inorganic radical; each R can be the same ordifferent; wherein each R¹ can be H or any organic or inorganic radical,each R¹ can be the same or different; x≧1; preferably x≧2;y has a valueof 0.5 for said reduced or nonoxidized form; y has a value from greaterthan 0.5 to 1 for said reduced form and y has a value from less than 0.5to 0 for said oxidized form.
 48. A method according to claim 1 whereinsaid polymer is a polyaniline having structural formula: ##STR2##wherein each R can be H or any organic or inorganic radical; each R canbe the same or different; wherein each R¹ can be H or any organic orinorganic radical, each R¹ can be the same or different; x≧1; preferablyx≧2;y has a value of 0.5 for said reduced or nonoxidized form; y has avalue from greater than 0.5 to 1 for said reduced form and y has a valuefrom less than 0.5 to 0 for said oxidized form.
 49. A method accordingto claim 1 wherein said article is stretch oriented.
 50. A methodaccording to claim 1 wherein said article is stretch oriented.